Eradicable carbon paper



United States Patent This invention relates to a pressure-sensitivetransfer paper commonly called carbon paper, and more particularly tosuch paper having a transfer medium which is capable of simple and easyeradication.

A simplified flow sheet of the method employed in producing the transferpaper is as follows:

Prepare aqueous solution of tannic acid, ferric chloride and potassiumcarbonate Filter and separate pigment residue Mix pigment thoroughlywith cane wax binder and carrier of oleic acid and mineral oil Applypigment mix conventionally to paper backing to producepressure-sensitive transfer paper Carbon papers, of course, have beenknown for many years in the field of typewriter supplies. The transfersurface on such paper usually comprises an ink pigment in a suitablebinder.

When carbon paper is employed to make additional copies of typewrittenmatter, there is little difiiculty in removing unwanted transfermaterial by erasing. However, recently carbon paper ribbons have beendeveloped for use with typewriters, particularly electric typewriters,to make the ribbon or original copy. The carbon paper ribbon has gainedin popularity because of the sharp and distinct imprint which ispossible as a result of the relatively stiff paper backing asdistinguished from the softer fabric ribbons. Further, the ink pigmenton the conventional carbon paper ribbons is dispersed in a hard carnaubawax binder which contributes to the sharpness and clarity of the typeimprint.

As is well known, removing the imprint from a fabric ribbon copy isconsiderably more difficult than removing the imprint from a carboncopy. The most common means for removing the ribbon copy imprint is theeraser. The chore of removing the transfer material from the ribbon copywhen an electric typewriter is used is aggravated because the imprint iscut deeper into the paper. As a result, erasing has become tedious andthe results of the erasure often distractful. The problem of erasing isfurther aggravated when carbon paper ribbon is employed, since theimprint is more bold and distinct than that produced by the fabricribbon.

An attempt has been made to find an eradicator for the ink pigment incarnauba wax, however, solvents of the pigment and carnauba wax eitherdamage or discolor the paper and are, therefore, unsatisfactory.

Accordingly, it is a primary object of the invention to provide a carbonpaper having a novel transfer material which is capable of simple andeasy eradication.

It is a further object of the invention to provide a carbon papertypewriter ribbon having a transfer surface which is amenable toeradication.

It is a feature of this invention to provide a novel liquid eradicatorwhich eradicates the transfer material but which does not damage the"paper and which leaves the paper in condition for immediate use.

In accordance with a broad aspect of the invention, there is provided apaper backing faced with a layer of pressure-sensitive transfer materialcomprising ink pigment dispersed in a wax binder, the wax binder beingcharacterized by having an acid number between 25 and 35, asaponification number between 55 and 70, a resin content less than 3%,and an oil content less than 5%.

In accordance with a further aspect of the invention, the ink pigmentcomprises a reaction product of tannic acid, ferric chloride andpotassium carbonate.

The above mentioned and other features and objects of this invention andthe manner of attaining them will become more apparent and the inventionitself will be best understood by reference to the following descriptionof an embodiment of the invention.

The paper backing and the techniques for applying the transfer materialto the paper backing are conventional and will, therefore, not bedescribed.

The novel transfer material which is applied as facing to a paperbacking comprises an ink pigment consisting of a reaction product oftannic acid, ferric chloride and potassium carbonate. The constituentsare thoroughly mixed in distilled water and the proportions aredetermined by observing the color of the filtrate during the removal ofthe water by filtering. Empirically, it has been found that the mostsatisfactory proportion of constituents is that which produces a clearfiltrate. For example, a preferred composition comprises approximatelythe following parts by weight:

The pigment residue, in powder form, is mixed with a cane wax binderhaving the following characteristics: A melting point of 171 to 176 F.,a penetration of 3 maximum, an acid number of between 25 and 35, asaponification number of between 55 and 70, an ash content of less than0.5%, a resin content less than 3% and an oil content of less than 5%.The pigment and wax binder are mixed thoroughly at a temperatureslightly higher than the melting temperature of the wax, and to thismixture is added a carrier comprising oleic acid commonly called redoil, and a mineral oil commonly called white oil. This mixture ofpigment, binder and carrier is mixed thoroughly and applied in theconventional way to the paper backing.

-In accordance with a preferred composition, the ingredients whichconsist essentially of the pigment, carrier and binder are mixedtogether in approximately equal portions, the oleic acid constitutingapproximately 7% by weight of the carrier.

The novel eradicator which is capable of dissolving the wax anderadicating the pigment comprises an aqueous solution containingapproximately 2% by volume of citric acid, and a separate solution ofsodium hypochlorite. The sodium hypochlorite solution serves primarilyas a bleach. Preferably, in eradicating the transfer material, thesodium hypochlorite is first applied in a small amount to the transfermaterial and then the diluted solution of citric acid is applied to thesodium hypochlorite. The dissolved wax and pigment are then removed fromthe paper by blotting in the conventional way.

While the foregoing description sets forth the principles of theinvention in connection with specific materials, it is to be understoodthat this description is made only by way of example and not as alimitation of the scope of the invention as set forth in the objectsthereof and in the accompanying claims.

What is claimed is:

1. A pressure-sensitive transfer paper faced with a layer of transfermaterial amenable to eradication consisting essentially of an inkpigment formed of a reaction product of tannic acid, ferric chloride andpotassium carbonate dispersed in a cane wax binder having an acid numberranging from about 25 to 35, a melting point of about 171 F. to 176 F.,a penetration of 3 maximum, a saponification number ranging from about55 to 70, an ash content of less than 0.5%, a resin content less than 3%and an oil content less than 5 said ink pigment and wax also havingmixed therewith a carrier comprising oleic acid and mineral oil, theproportion of the pigment, the wax binder and the carrier beingapproximately equal.

2. A pressure-sensitive transfer paper faced witha layer of transfermaterial amenable to eradication consisting essentially of an inkpigment formed of a reaction product of approximately 3.79 parts byweight of tannic acid, 3.2 parts by weight of ferric chloride, and 2.36parts by weight of potassium carbonate dispersed in a cane wax binderhaving an acid number ranging from about 25 to 35, a melting point ofabout 171 F. to 176 F., a penetration number of 3 maximum, asaponification number ranging from about 55 to 70, an ash content ofless than 0.5%, a resin content less than 3% and an oil content lessthan 5%, said ink pigment and wax also having mixed therewith a carriercomprising oleic acid and mineral oil, the proportion of the pigment,the wax binder and the carrier being approximately equal,

the oleic acid constituting approximately 7% of the car- ,rier.

3. A method for treating a selected area of a surface containing animprint of an ink pigment and remove the same, said ink pigmentconsisting essentially of a reaction product of tannic acid, ferricchloride and potassium carbonate dispersed through a cane wax binderhaving an acid number ranging from about 25 to 35, a melting point ofabout 171 F. to 176 F., a penetration of 3 maximum, a saponificationnumber ranging from about to 70, a resin content less than 3% and an oilcontent less than 5%, said ink pigment and wax also having mixedtherewith a carrier comprising oleic acid and mineral oil, theproportion of the pigment, the wax binder and the carrier beingapproximately equal, which comprises, treating the selected areacontaining said impressed ink pigment with a solution of sodiumhypochlorite, contacting the treated selected area with a dilute aqueoussolution of citric acid, and then blotting said area to remove thedissolved wax and pigment.

References Cited in the file of this patent UNITED STATES PATENTS1,905,118 Nadell Apr. 25, 1933 2,559,608 Ehrlich July 10, 1951 2,589,306Steiner Mar. 18, 1952 2,682,516 Wilder et al. June 29, 1954 2,824,812Drautz Feb. 25, 1958 2,836,152 Rosenblum May 27, 1958 2,955,958 BrownOct. 11, 1960 OTHER REFERENCES Karrer: Organic Chemistry, 2 ed., 1946,p. 530. Mosher: Specialty Papers, 1950, pp. 345-354.

1. A PRESSURE-SENSITIVE TRANSFER PAPER FACED WITH A LAYER OF TRANSFERMATERIAL AMENABLE TO ERADICATION CONSISTING ESSENTIALLY OF AN INKPIGMENT FORMED OF A REACTION PRODUCT OOF TANNIC ACID, FERRIC CHLORIDEAND POTASSIUM CARBONATE DISPERSED IN A CANE WAX BINDER HAVING AN ACIDNUMBER RANGING FROM ABOUT 25 TO 35, A MELTING POINT OF ABOUT 171*F. TO176*F., A PENETRATION OF 3 MAXIMUM, A SAPONIFFICATION NUMBER RANGINGFROM ABOUT 55 TO 70, AN ASH CONTENT OF LESS THAN 0.5%, A RESIN CONTENTLESS THAN 3% AND AN OIL CONTENT LESS THAN 5%, SAID INK PIGMENT AND WAXALSO HAVING MIXED THEREWITH A CARRIER COMPRISING OLEIC ACID AND MINERALOIL, THE PROPORTION OF THE PIGMENT, THE WAX BINDER AND THE CARRIER BEINGAPPROXIMATELY EQUAL.